Heretofore, monolithic glass plates have been used as the windowpanes of vehicles. The inner face of a vehicle windowpane has to be protected from burring, and the air-heating and air-cooling efficiency of the vehicle interior is to be improved. Therefore, a certain proposal was made to use a double-layer window glass (exemplified in Patent Reference 1, listed below). According to this proposal, two glass plates are fixed one on another, with a hollow space being defined between them.
The outer face of a vehicle windowpane is exposed to the outside, and consequently more prone to become dirty. Whether the glass plates are of a single-layer or double-layer structure, the outer glass faces exposed to the exterior of vehicles have been cleaned using motor-driven and mechanical rubber wipers.
Instead of using such motor-driven rubber wipers, air wipers of some types (see Patent References 2 and 3) were proposed for use to clean up the outer glass faces exposed to the exterior of vehicles.
A driving mechanism such as those used to rotate the mechanical wipers can be dispensed with in the air wipers, thereby rendering them simpler in structure. The air wipers do not require replacement of torn-off wiping elements, contrary to a case wherein the mechanical rubber wipers are employed. Any element of each air wiper is not kept in contact with the glass plate surface and does not repeat reciprocation. Thus, this glass face will be protected from being scratched. Any washing liquid (i.e., detergent solution) that has been inevitable to the rubber wipers is no longer necessary. Such air wipers are less likely to cause environmental pollution.
However, jet nozzles for blowing off a highly compressed air should be disposed at peripheral zones (particular, near a lower edge) of the front glass, rear glass or the like. Due to such a requirement for ensuring a good sight, an area which the compressed air jet can wipe is limited to a narrow region located near the jet nozzle. In other words, the air wiper can not necessarily wipe uniformly over the entire surface of a windowpane.
In another proposal (see Patent Reference 4) made to more widely wipe a windowpane, a number of air jet holes are formed in a wiper body. This body is driven to reciprocate on and along the outer surface of a windowpane. Air is jet out through the holes towards said surface so as to blow off rainwater or the like.
Further, some multilayer glass plates have been proposed (as exemplified in Patent Reference 5) for use as buildings' windowpanes and for example for the purpose of providing an adiabatic effect.
Also in case of the buildings' windowpanes, their outer surfaces exposed to the outside are prone to rapidly become dirty. Such outer surfaces have been cleaned almost by hand.    Patent Reference 1: Patent Laying-Open Gazette No. 6-227250    Patent Reference 2: ibid. No. 07-040806    Patent Reference 3: ibid. No. 2002-79919    Patent Reference 4: ibid. No. 2003-118546    Patent Reference 5: ibid. No. 2005-060141